Well? - attempting to sort out your dissociated comments, bringing Canada in as an unrelated country to this subject, I will tell you that all the touchy feely emotions are rendered irrelevant because the US, America (if you will), is a country and society of laws, and the plain, unabashed fact undisputed by any legal authority, is that crossing into the US illegally is a crime. All the smooze, touchy feely emotions etc is a mask to cover the reality of that fact that there is essentially an "invasion" of illegals into the US - which is increasing in an attempt to swamp, overcome if you will, the border security.
NOTE: On a specific note, Frum was attached to the Bush administration - not really a proforma validation of Conservatism, maybe a member of the Republican establishment, but not Conservatism I can assure you.
PS: Here's something most folks don't know, the legal immigration system in the US was mostly shut down from the mid 20's until the early 60's - for one simple reason, to allow assimilation of incoming non-Americans.
I assume you live in MX, I lived there, let me assure you the current "crop of immigrants" has little or no interest in assimilating into the American culture. They are there, by their own admissions, to access a "better life" etc. In other words, they seek the easy life, the milk, the gold and are unwilling to follow the previous generations path that came to America to find those same things, but learned the language, that assimilated into the American culture and knew that doing so causes a rising tide that floats all boats including their children and prodigy.